Otoacoustic emissions provide a non- invasive window into cochlear function, being presumably a by-product of the action of the cochlear amplifier. This study aims to use otoacoustic emissions to examine the question of propagation time along the cochlear partition; i.e., does the delay of the emission essentially reflect the delay associated with the action of the cochlear mechanical amplifier? The group delay of amplitude- modulated tone-burst evoked otoacoustic emissions will be measured in guinea pigs and humans, the guinea pig data compared with basilar membrane data in an attempt to delineate a "propagation component", if it exists. This study will also compare measured group delay values with phase-gradient estimate of delays obtained using distortion product otoacoustic emission sweep-frequency paradigms, the thesis being that such paradigms do not provide for travel times within the cochlea.